Newsgroups: comp.robotics
Path: brunix!doorknob!kwh
From: kwh@cs.brown.edu (Kwun Han)
Subject: Re: PLCC wire wrap socket source needed
In-Reply-To: nstn@quercus.gsfc.nasa.gov's message of 7 Dec 1993 21:51:08 GMT
Message-ID: <KWH.93Dec7172641@tahoe.cs.brown.edu>
Sender: news@cs.brown.edu
Organization: Dept. of Computer Science, Brown University
References: <mRYlXl.eW4@asic.sc.ti.com> <BILLW.93Dec7122529@glare.cisco.com>
	<2e2tsc$aru@skates.gsfc.nasa.gov>
Date: Tue, 7 Dec 1993 22:26:41 GMT
Lines: 36

In article <2e2tsc$aru@skates.gsfc.nasa.gov> nstn@quercus.gsfc.nasa.gov (Nathan Stratton) writes:
   I have a small problem I cant get this 74ls14 to give me a high and low
   signal.

   {                           O +5 VDC
   {                           | 
   {                           |
   {                           /
   {                           \
   {   FROM                    /  220 K
   {  ENCODER  |\              \
   {         3 | \             |         74LS14
   {    -------|   \           |        |\ 
   {           | 741 \_________|________| \____ OUTPU
   {    -------|     /         |        | /
   {    |      |   /           |        |/
   {    |    2 | /             | 
   {    |      |/              V led 
   5V   |                      -
   O-/\/\/\---|                |   
   {          |                |
      100 K   |                |
	      |                |
	      O GND            O GND

	      I get a low on the output of the 74ls14 when the input moves high
	      to low. If I ground the input of the 74ls14 I get a high output.
	      What is wrong???

	Did you measure the voltage at the output of the 741? Most
Opamps are pretty crappy and doesn't go all the way down to the
negative supply voltage when the output is low. You may get some weird
value at the transition of the 74LS, also, consider using a CMOS chip.
They have a better threshold value.

Kwun
